After conducting the first step of DNA testing, wildlife biologists from the University of California, Davis, determined that the fox seen near Donner Lake in recent weeks contains the genes of a non-native red fox somewhere in its maternal line — as opposed to the highly endangered Sierra Nevada red fox, of which there may be fewer than 50 remaining.

"It's not a good sign," said Dr. Ben Sacks of UC Davis, who studies fox populations along with grad student Cate Quinn. "The fact that it shows non-native is discouraging. But we don't want to jump to any premature conclusions."

The fox in question was first reported to the California Department of Fish and Wildlife on Thursday, Oct. 31. It has since been seen on multiple occasions along the north shore of the lake.

Quinn, who is currently studying one of only two known populations of the Sierra Nevada red fox, near Sonora Pass, collected scat, hair and saliva samples from the animal last week. The mitochondrial DNA from the scat revealed maternal genetics from a non-native red fox, which reside in the San Joaquin Valley and foothills but are not known to venture into the Sierra Nevada.

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Sacks said the mitochondrial DNA, which determines female lineage only, could trace back to the previous generation or many generations. If the female, non-native red fox genes that were discovered prove to be many generations removed, a small chance remains that the animal is close to a 100 percent indigenous Sierra Nevada red fox.

"It could be a first-generation hybrid, which, from a management point of view, is essentially a non-native — maybe worse, because it means that there are some non-natives maybe circulating through the native populations," Sacks said. "But if it's sort of a multi-generational back cross, then really for all intents and purposes, it's native.

"It could be essentially 100 percent native … and at some point there was some non-native introgression."

In order to make that distinction, Sacks said the animal's nuclear DNA — from both the males and females in its family line — will be tested as well, which could take a month or longer.

While researchers are unsure how the fox arrived at Donner Lake, where it seems comfortable and relatively undaunted by human activity, Sacks said it may have wandered up from the valley along the Interstate 80 corridor or was brought to the area by someone.

"They're pretty solitary. If this fox made its way up there on its own, or was dropped off, my guess is that it's all by itself — because as far as we know, there are no other foxes in the area," Sacks said, adding that his biggest concern is that the fox, if truly non-native, might find one of the small populations of indigenous Sierra Nevada red foxes and interbreed (native foxes also have been found near Mount Lassen). "If he starts to get especially disappointed (in not finding a mate) and starts wandering, he might well find the population 50 miles to the south. And that would be a problem. There are many kinds of negative genetic effects from taking a non-native individual and introducing it to a small, endangered gene pool.